This invention relates to respiration assemblies and to indicators.
The invention is more particularly concerned with assemblies with provision for detecting correct placement of an endotracheal tube or for indicating patient breathing.
One of the major problems associated with the use of an endotracheal tube is that of ensuring that the patient end of the tube is correctly located in the trachea and not in the esophagus. There are various ways in which correct intubation can be detected. The usual way is to connect the machine end of the tube to a capnograph, which is responsive to the levels of carbon dioxide. When the tube is correctly inserted, the level of carbon dioxide detected will rise and fall with the patient""s breathing. By detecting this alternating level of carbon dioxide, correct intubation is indicated. If the tube is incorrectly inserted, in the oesophagus, any carbon dioxide produced by the digestive system will be at a relatively steady level. Capnographs can produce a reliable indication of correct intubation but the equipment is relatively bulky and expensive so it is only available in well-equipped surgical operating theatres.
An alternative device can be used to detect carbon dioxide, which includes a chemical color-change indicator, such as described in, for example, WO96/24054, EP509998, U.S. Pat. Nos. 5005572, 4879999, EP257916, U.S. Pat. Nos. 4691701, 4790327, WO89/07956, GB2218515 and U.S. Pat. No. 4728499. This form of device usually comprises a paper or some other substrate that is impregnated or coated with the chemical including a pH-sensitive indicator dye, the substrate preferably being provided in some form of transparent connector attached to the machine end of the tube. Such indicators can be of low cost and can provide a clear indication that the tube has been correctly inserted. If the indicator fails to change color, the clinician knows immediately that the tube has been incorrectly inserted. These prior indicators are designed to be left in position on the connector during use of the tube. This can, however, be a disadvantage because, to be effective, the indicator must be exposed to the maximum gas flow, thereby inevitably providing some impediment to gas flow. Also, where the indicator is positioned in the main gas flow path, this may prevent access to the tube, such as by a suction catheter or the like.
It is also useful in some circumstances to have a readily visible indicator confirming that the patient is breathing on other respiration devices, such as face masks or the like.
It is an object of the present invention to provide an improved respiration assembly and indicator.
According to one aspect of the present invention there is provided a respiration assembly including a respiration device, a housing mounted with the respiration device and an indicator assembly mounted in the housing, the indicator assembly having an indicator element mounted to extend within a lumen through the housing, and the indicator assembly being detachably secured in the housing such that the indicator assembly can be removed from the machine end of the housing.
The housing is preferably of a transparent plastics material and is preferably a connector. The indicator assembly is preferably shaped to prevent the connector mating with another connector while the indicator assembly is secured with the connector. The indicator assembly may be a push fit in the machine end of the housing. The indicator assembly preferably comprises a frame and an indicator element supported on the frame. The frame may comprise a circular ring attached coaxially with one end of the housing and a projecting member extending substantially axially of the housing, the indicator element being supported on the projecting member. The indicator element is preferably of a paper including a carbon-dioxide color-change indicator chemical. The indicator assembly preferably includes a handle extending along the outside of the housing by which the indicator assembly can be gripped to remove it from the housing. The respiration device may be an endotracheal tube.
According to another aspect of the present invention there is provided an indicator for indicating patient breathing, the indicator having an outer housing adapted for connection at one end to a respiration device and an indicator assembly detachably secured in the housing and removable from the opposite end of the housing.
According to a further aspect of the present invention there is provided a method of determining correct intubation of a patient comprising the steps of introducing into the trachea of the patient an endotracheal tube assembly of the kind including an endotracheal tube, a connector mounted at the patient end of the tube and an indicator assembly mounted in the connector, observing the indicator assembly to ensure correct intubation, and subsequently removing the indicator assembly from the connector while leaving the connector in position on the tube.
An endotracheal tube assembly and its method of use, in accordance with the present invention, will now be described, by way of example.